1. Technical Field
The present invention relates to a resonator element, a gyro sensor element, an electronic device, an electronic apparatus, and a moving object.
2. Related Art
In the related art, a resonator element or a gyro sensor element is used for an electronic apparatus such as a mobile phone or a digital camera, and a moving object such as an automobile. According to a demand for a high performance of the electronic apparatus or the moving object, low impedance or an improvement in detection sensitivity is required for the resonator element or the gyro sensor element. For example, in JP-A-2002-261576, a resonator piece is disclosed in which a rigidity reinforcement portion reinforcing a through groove and the through groove are disposed in a driving arm portion. In addition, in JP-A-2006-208261, an inertial sensor is disclosed in which a plurality of through holes is arranged in a driving arm portion for excitation. A resonator piece and an inertial sensor are known in which rigidity of the driving arm increases due to such a configuration, and impedance (a CI value, and series equivalent resistance) is able to be decreased by forming an electrode for excitation in a side surface of the driving arm, and a side surface of the through groove or the through hole facing the side surface of the driving arm.
However, recently, downsizing of the resonator element or the gyro sensor element has progressed, and a width of the driving arm has been remarkably narrowed. The through hole disposed for decreasing the impedance of the element is also narrowed, and thus it is difficult to dispose the through hole having a large opening area. In contrast, broadening a width dimension of the driving arm and enlarging the through hole may be considered. However, when the width of the driving arm is W, and a length of the driving arm is L, a vibrational frequency f of the driving arm has to satisfy the following relationship.f∝W/L2  Expression 1
For this reason, the length of the driving arm has to be elongated as the width of the driving arm becomes broader, and thus external dimensions of the driving arm increase. That is, it is difficult to provide a resonator element and a gyro sensor element having low impedance in a small size.